The objectives of this study are to evaluate the use of recombinant human tumor necrosis factor (rHuTNF) in treating patients with refractory pleural effusions and ascites to determine the safety and biologic effects of this treatment. Pharmacokinetics and immunologic potential of intracavitary administration of rHuTNF in patients with malignant pleural effusion and/or malignant ascites will be assessed.